curriculum/challenges/english/blocks/learn-special-methods-by-building-a-vector-space/65fa9e1b6c6db919385359ec.md
The special method __mul__ can be implemented to specify what should happen when the current instance is multiplied by another object.
Create an empty __mul__ method within the R2Vector class and give it two parameters: self, and other.
You should define a __mul__ method within the R2Vector class.
({
test: () => assert(runPython(`
_Node(_code).find_class("R2Vector").has_function("__mul__")
`))
})
Your __mul__ method should have two parameters, self and other.
({
test: () => assert(runPython(`
_Node(_code).find_class("R2Vector").find_function("__mul__").has_args("self, other")
`))
})
class R2Vector:
def __init__(self, *, x, y):
self.x = x
self.y = y
def norm(self):
return sum(val**2 for val in vars(self).values())**0.5
def __str__(self):
return str(tuple(getattr(self, i) for i in vars(self)))
def __repr__(self):
arg_list = [f'{key}={val}' for key, val in vars(self).items()]
args = ', '.join(arg_list)
return f'{self.__class__.__name__}({args})'
def __add__(self, other):
if type(self) != type(other):
return NotImplemented
kwargs = {i: getattr(self, i) + getattr(other, i) for i in vars(self)}
return self.__class__(**kwargs)
def __sub__(self, other):
if type(self) != type(other):
return NotImplemented
kwargs = {i: getattr(self, i) - getattr(other, i) for i in vars(self)}
return self.__class__(**kwargs)
--fcc-editable-region--
--fcc-editable-region--
class R3Vector(R2Vector):
def __init__(self, *, x, y, z):
super().__init__(x=x, y=y)
self.z = z
v1 = R2Vector(x=2, y=3)
v2 = R2Vector(x=0.5, y=1.25)
print(f'v1 = {v1}')
print(f'v2 = {v2}')
v3 = v1 + v2
print(f'v1 + v2 = {v3}')
v4 = v1 - v2
print(f'v1 - v2 = {v4}')